Battery system with thermal control loop

ABSTRACT

A battery cell system includes a plurality of battery cells having an annular shape abutting one another to form a battery cell stack with an annular shape to facilitate cooling. The battery cell system includes a stack interface having an annular housing operatively connected to the plurality of battery cells. A cooling loop is defined about the battery cell stack and the stack interface and through central through holes of the battery cell stack and the stack interface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalApplication No. 63/084,341, filed Sep. 28, 2020, the entire contents ofwhich are herein incorporated by reference in their entirety.

BACKGROUND 1. Field

The present disclosure relates to energy storage such as batteries, andmore particularly to energy storage such as batteries for use inaircraft, including more-electric, hybrid-electric, and full-electricaircraft.

2. Description of Related Art

High-energy dense battery cells for use on hybrid electric or fullelectric aircraft, such as lithium ion (Li-Ion) cells, can potentiallypose a fire hazard risk due to thermal runaway between the anode andcathode active materials. Additionally, high-energy dense batteries havenumerous inherent failure modes inside the cell. When considering theuse of such cells for aviation, hundreds of cells, if not more, aretraditionally used to meet system voltage and energy requirements. Theneed for reliability and safety tends to result in high-weight systems,which can be undesirable in aerospace applications.

The conventional techniques have been considered satisfactory for theirintended purpose. However, there is an ever present need for improvedsystems and methods for packaging and using high specific energy batterycells in a safe manner with reduced weight. This disclosure provides asolution for this need.

SUMMARY

A battery cell system includes a plurality of battery cells having anannular shape abutting one another to form a battery cell stack with anannular shape to facilitate cooling. The battery cell system includes astack interface having an annular housing operatively connected to theplurality of battery cells. A cooling loop is defined about the batterycell stack and the stack interface and through central through holes ofthe battery cell stack and the stack interface.

In accordance with some embodiments, the system includes a first annularmetallic conductor positioned at a first end of the battery cell stackand a second annular metallic conductor positioned at a second end ofthe battery cell stack. The system can include a plurality of sensorspositioned within at least one of the battery cells. The plurality ofsensors can include at least one of a temperature sensor, a voltagesensor, and a pressure sensor. The plurality of sensors can beoperatively connected to a battery management system (BMS).

The battery cells can be hermetically sealed. The battery cell stack isa 520 volt stack and includes 145 battery cells. The stack interface caninclude a plurality of heat dissipating field effect transistors (FETs).The stack interface can define an inner perimeter and an outerperimeter. The heat dissipating FETs can be positioned more proximate tothe outer perimeter than the inner perimeter and are circumferentiallyspaced apart along the outer perimeter. The stack interface can includea mechanical switch device configured and adapted to selectively connector disconnect one of the battery cell stack from an adjacent batterycell stack.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1A is a schematic cross-sectional side perspective view of abattery cell system constructed in accordance with the presentdisclosure, showing the stacks of cells, main BMS and stack interfaces;

FIG. 1B is an exploded perspective view of a portion of the battery cellsystem of FIG. 1A, showing a portion of the battery cell stack, aconductor and a stack interface;

FIG. 2 is a schematic side perspective view of a portion of the batterycell system of FIG. 1A, showing one of the stacks of cells and the mainBMS shown partially removed therefrom; and

FIG. 3 is a schematic perspective view of another embodiment of abattery cell system constructed in accordance with the presentdisclosure, showing five stacks of cells.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, a partial view of an embodiment of a system in accordancewith the disclosure is shown in FIG. 1A and is designated generally byreference character 100. Other embodiments of systems in accordance withthe disclosure, or aspects thereof, are provided in FIGS. 1B-3, as willbe described. The systems and methods described herein can providebattery systems with improved communication, components having anannular shape to improve thermal control, and improved cooling to notonly cool a battery cell or system, but also target and prevent and/orextinguish a battery thermal runaway in volume and weight sensitiveapplications.

As shown in FIGS. 1A-1B, a battery system 100 includes a plurality ofannular battery cells 104 abutting one another to form a battery cellstack 102. System 100 includes a plurality of battery cell stacks 102,e.g. stacks of battery cells 104. A housing 131 of each battery cell 104is shaped as a shallow cylindrical annulus and abut one another to forma given stack 102 with an annular shape, e.g. a cylindrical annulus, tofacilitate cooling. A main battery management system (BMS) 106 isoperatively connected to at least one of the stacks 102 of battery cells104. The main BMS 106 includes an annular housing 108, e.g. shaped as ashallow cylindrical annulus, and a motor drive assembly 110 positionedwithin an inner diameter hole 112 of the annular housing 108 configuredand adapted to drive circulation of a heat transfer fluid around theplurality of stacks 102. The motor drive assembly 110 includes a fan 115or other fluid mover to effect the movement. The motor drive assembly110 and main BMS manages thermal stability of the system 100. Thebattery system 100 includes system housing 130 that surrounds theplurality of stacks 102 and the main BMS 106. The main BMS 106 ismodular and can be added to the front and/or rear of the housing 130 asneeded to achieve proper levels of redundancy. The main BMS 106 isoperatively connected to each stack interface 114, as described in moredetail below.

As shown in FIG. 2, the battery system 100 includes a fluid-to-fluidheat exchanger matrix 151 inside the inner diameter hole 112 to eithertransfer heat into the heat transfer fluid within housing 130 forbattery cell stack warming, or out of the fluid for battery cell stackcooling. As fluid is drawn through inner diameter hole 112 by fan 115(which is downstream from heat exchanger matrix 151) the fluid withinhousing 130 is heated or cooled by the fluid within the heat exchangematrix 151 (which is fluidically isolated from the fluid within housing130). The fluid in the heat exchanger matrix 151 is fluidicallyconnected to a source of heating outside of system 100 such as a thermalengine or electrical heater or a source of cooling such as a radiator,to enable the BMS to maintain stack temperatures within acceptablelimits.

With continued reference to FIGS. 1A-2, the battery system 100 includesa plurality of first annular metallic conductors 134 each positioned ata first end 136 of a respective stack 102 of battery cells 104 and aplurality of second annular metallic conductors 138 each positioned at asecond end 140 of a respective stack 102 of battery cells 104 of theplurality of stacks 102 of battery cells 104. Conductors 134 and 138serve as a contactor plate and pressure plate to provide a more evenlydistributed compression for the stack 102. Bolts or struts 137 arestrutted from one conductor 134 to the other 138 to force face contactbetween abutting cells 104 ensuring maximum contact surface is achieved.The annular shaped stack-up formed by the stack of battery cells 104,conductors 134 and 138, stack interfaces 114 (described below), and BMS106 defines a central hole 117 for carrying a heat transfer fluid and/orcoolant that creates a protective thermal barrier around all systemsurfaces in a thermal loop arrangement, as indicated schematically bythe flow arrows. The thermal loop goes through the center hole 117 ofthe stack-up and out one end, around an outer perimeter of the stack-up,between the stack-up and the housing 130, and around to the opposite endof the stack-up back through the center hole 117. This thermal loopenables rapid charge of the cells 104 and fire abatement.

As shown in FIG. 1B, battery cells 104 can include cooling fins, metalfoams or other surface projections 150 extending into the center hole117 or extending from the outer perimeter of cells 104 to improve heattransfer between the heat transfer liquid/coolant and the cells 104.Projections 150 can similarly be included on conductors 134/138 or stackinterfaces 114. In some embodiments, the heat transfer fluid can serveas coolant and fire arresting agent if/when the main BMS 106 detectsissues. Since the coolant and retardant are one and the same fluid, thebattery system 100 is lighter and simpler than systems where a separatecoolant supply and retardant supply are needed. The heat transfer fluidmaintains even thermal gradient enabling longer life and helps tomaintain state of health (SOH) for a longer life.

With reference now to FIGS. 1A-2, in the event of a thermal runaway of asingle cell 104 due to internal failure, the rate of transfer of heatfrom the cell 104 to the fluid would increase naturally without anyaction by the BMS 106 or the sBMS 126, due to the increased differencein temperature between the cell and the fluid. If the rate of coolingpossible with the cooling projections 150, e.g. fins, metal foam, etc.,and normal fluid circulation rate is insufficient and the BMS 106 orsBMS 126 detects a problem a method of controlling heat transfer in abattery system is available. A method of controlling heat transfer in abattery system, e.g. battery system 100, includes monitoring at leastone characteristic of a battery cell, e.g. battery cell 104, within thebattery system with a battery management system (BMS), e.g. main BMS 106or sBMS 126.

With continued reference to FIGS. 1A-2, the method includes sendinginformation from the at least one sensor to the BMS with an opticalcommunication link, e.g. optical communication link 107. The opticalcommunication link is connected to each of the plurality of batterycells. The method includes selectively varying a fluid circulation ratein the battery system with the BMS depending on the at least onecharacteristic. Selectively varying the fluid circulation rate includesincreasing the fluid circulation rate with the BMS if at least one ofthe at least one characteristic indicates thermal runaway in the batterycell to increase. In this way, the BMS acts to increase the coolingavailable and minimize propagation of thermal runaway to another batterycell within the battery system. Increasing the fluid circulation rateincludes sending a rate increase signal from the BMS to a motor driveassembly, e.g. motor drive assembly 110, having a fluid mover, e.g. fan115, propeller, or the like, to increase a circulation rate of a heattransfer fluid within the battery system. Selectively varying the fluidcirculation rate in the battery system includes decreasing the fluidcirculation rate with the BMS if at least one of the characteristicsindicates a low temperature in the battery cell. The characteristics ofthe battery cell include at least one of electrical characteristics(e.g. voltage), temperature, pressure, or the presence of characteristicgases. These characteristics can be measured with sensors, e.g. sensors128, which are described in more detail below.

As shown in FIG. 1A, the system housing 130 forms a pill-shaped pod 101with an outer surface 132 free of vertices, except for the features thatmay be required for mounting and attaching the battery system. Pod 101can also be a cylindrical shape, which is similar to the pill shapeshown except that the pod 101 would have flat ends instead of thearcuate ends. The aerodynamic structure allows for maximum scalability,modularization, and thermal control. The aerodynamic shape permitsplacement of system 100 exterior to the fuselage, e.g. on a wing, orinterior. Those skilled in the art will readily appreciate that avariety of aerodynamic housings can be used. Housing 130 includesremovable end caps 133 to allow for stack 102 replacement. Stack 102 isremovable from housing 130 and cells 104 are removable from the stack102.

With reference now to FIGS. 1A-2, the battery system 100 includes stackinterfaces 114 having an annular shape, e.g. shaped as a shallowcylindrical annulus. Each stack interface 114 has an annular housing andis operatively connected to an end 116 of a respective stack 102 and isoperatively connected to the battery cells 104 in the stack 102. Theannular housing defines a center (aligned with longitudinal axis A) andan outer perimeter 122. A cooling loop is defined about each batterycell stack 102 and its respective stack interface 114 and throughcentral through holes 117 of the battery cell stack 102 and the stackinterface 114. Each stack interface 114 includes a plurality of heatdissipating field effect transistors (FETs) 118. Each stack interface114 includes an inner perimeter 120. The heat dissipating FETs 118 arepositioned more proximate to the outer perimeter 122 than the innerperimeter 120 and/or the center and are circumferentially spaced apartalong the outer perimeter 122 about a stack axis A. The FETs 118dissipate heat in a more efficient manner due to their placement alongthe outer perimeter 122. Each stack interface 114 acts as an isolationplate and includes at least one mechanical switch device 124, such as achemically and/or thermally activated/deactivated mechanical contactorconfigured and adapted to selectively connect or disconnect one of thestacks 102 of battery cells 104 from other adjacent stacks 102 ofbattery cells 104. The mechanical switch device 124 is intrinsic to thestack interface 114 and the position therein can vary depending on thespecific design of stack interface 114. The isolation plate ispositioned between each stack assembly (module) and houses themechanical switch devices 124. The mechanical switch device 124 (asopposed to electrical switches, or the like) permits reliable and quickautomatic high-voltage disconnect and lock-out.

As shown in FIG. 2, each stack interface 114 includes a BMS, e.g. asecondary battery management system (sBMS) 126. The sBMS is operativelyconnected to a plurality of sensors 128 positioned within the housing131 of each battery cell 104 and the main BMS 106 either by way of asingle optical communication link 107 or by conventional electricalconnections. Sensors 128 are configured and adapted to send dataregarding at least one characteristic of a given battery cell 104 tosBMS 126 and/or the main BMS 106. Sensors 128 within each cell 104enable cell monitoring of every cell 104 in the system, which permitsearly detection of thermal runaway or other failure modes. Opticalcommunication link 107 reduces weight and increases ease of assembly asthere are no high-voltage flex cables or wire harnesses required. Thesensors 128 can include one or more of temperature, particulate/gasmonitoring devices, voltage and/or pressure sensors and they areintegrated within the cell itself. Additional sensors 128 can bepositioned outside of cells 104. Cells 104 are hermetically sealed andinclude glass feed-throughs for communications isolation.

With continued reference to FIG. 2, optical communication link 107 isoperatively connected to each battery cell 104 in a stack 102 tocommunicate signals (information or power) from sensors 128 within eachcell 104 via optical cable to the sBMS 126 and/or from the sBMS 126 tosensors 128. The sBMS 126 can provide processing and/or signalconditioning to the signals from sensors 128. The sBMS 126 is thenconnected to the main BMS via optical, wireless or other form ofcommunication link. That way, the main BMS 106 is operatively connectedto at least one sensor 128 within at least one of the battery cells 104via the sBMS for a given stack 102 and can monitor multiple stacks 102.The optical communication link 107 is connected to the sBMS 126 and thento the main BMS 106 in FIGS. 1 and 2, but it is also contemplated thatoptical communication link 107 can connect sensors 128 directly to themain BMS 106. The main BMS 106 identifies a failure mode and theappropriate corrective action that can be taken, e.g., increasedcooling, repair, mechanical disconnect, or the like.

A method for detecting an mitigating failure modes in a battery cell,e.g. battery cell 104, includes reading a battery cell characteristicwith a sensor, e.g. sensor 128, positioned within an outer housing, e.g.outer housing 131, of the battery cell. The method includes sending thebattery cell characteristic to a battery management system (BMS), e.g.BMS 106 and/or sBMS 126. The method includes determining whether thebattery cell characteristic meets a criteria with the BMS. The methodincludes signaling a failure mode if the battery cell characteristicdoes not meet the criteria. The method can include initiating adisconnect between the subject stack of battery cells, e.g. stack 102,and a remaining portion of the stacks of battery cells, or othermaintenance action, if the failure mode is signaled.

As shown in FIG. 1A, the battery system 100 includes a second systemhousing 130 that surrounds a second set of the plurality of stacks 102and a second main BMS 106 to form a second battery pod 103. The secondset of the plurality of stacks 102 is the same as the first, and thesecond main BMS 106 is also the same as the first main BMS. The secondbattery pod 103 is connected to the first battery pod 101 in series.

As shown in FIG. 3, in accordance with high voltage applications,another embodiment of system 100 includes five stacks 102 of batterycells 104 in a given pod. Each stack 102 uses sufficient number of cells104 connected in series to meet the system voltage requirement, andother strings or stacks of cells are electrically connected in parallelto respect the cell power limits and energy requirements of theapplication. For example, in one embodiment, a 520 volt stack caninclude 145 cells (for sake of clarity not all cells are shown stacked).With this modular set up, a single pod weighs about 1600 pounds andprovides about 130 kWh. With two pods connected in series with a similarstack and cell quantity, 1040V and 260 kWh can be provided to a givenload. Each cell stack 102 is modular in nature and the cell count withineach stack can be adjusted to meet system voltage and capacityrequirements. Cells 104 in a given stack can be replaced as-needed withnew cells 104 and the electrodes (metallic conductors 134, 138) can bereused. In FIG. 3 the main BMS 106, housing 130, stack interface 114 andflow of the thermal loop is not depicted for sake of clarity, but itwould be similar to that of FIG. 1A.

The methods and systems of the present disclosure, as described aboveand shown in the drawings, provide for more reliable, lighter weight,high-voltage power supplies that are scalable and modular for increasedflexibility. While the apparatus and methods of the subject disclosurehave been shown and described with reference to preferred embodiments,those skilled in the art will readily appreciate that changes and/ormodifications may be made thereto without departing from the scope ofthe subject disclosure.

What is claimed is:
 1. A battery cell system comprising: a plurality ofbattery cells having an annular shape abutting one another to form abattery cell stack with an annular shape to facilitate cooling; and astack interface having an annular housing operatively connected to theplurality of battery cells, wherein a cooling loop is defined about thebattery cell stack and the stack interface and through central throughholes of the battery cell stack and the stack interface.
 2. The batterycell system as recited in claim 1, further comprising a first annularmetallic conductor positioned at a first end of the battery cell stackand a second annular metallic conductor positioned at a second end ofthe battery cell stack.
 3. The battery cell system as recited in claim1, further comprising a plurality of sensors positioned within at leastone of the battery cells.
 4. The battery cell system as recited in claim3, wherein the plurality of sensors includes at least one of atemperature sensor, a voltage sensor, and a pressure sensor.
 5. Thebattery cell system as recited in claim 3, wherein the plurality ofsensors are operatively connected to a battery management system (BMS).6. The battery cell system as recited in claim 1, wherein the batterycells are hermetically sealed.
 7. The battery cell system as recited inclaim 1, wherein the battery cell stack is a 520 volt stack and includes145 battery cells.
 8. The battery cell system as recited in claim 1,wherein the stack interface includes a plurality of heat dissipatingfield effect transistors (FETs).
 9. The battery cell system as recitedin claim 8, wherein the stack interface defines an inner perimeter andan outer perimeter, wherein the heat dissipating FETs are positionedmore proximate to the outer perimeter than the inner perimeter and arecircumferentially spaced apart along the outer perimeter.
 10. Thebattery cell system as recited in claim 1, wherein the stack interfaceincludes a mechanical switch device configured and adapted toselectively connect or disconnect one of the battery cell stack from anadjacent battery cell stack.